Efficient synthesis of 11-cis-retinoids

The light sensitivity and unstable nature of 11-cis-retinoids makes them id eal visual chromophores in nature. The synthesis of 11-cis-retinal analogue s is of paramount importance in bioorganic studies of rhodopsin, the photor eceptor of the visual transduction pathway, but the instability of 11-cis-r etinoids complicates their synthesis and there is no general synthetic rout e. Common strategies to the cis geometry have failed in the case of 11-cis- retinoids, and most often low yields and complex isomeric mixtures are obta ined. Herein we report an efficient, general, and mild preparation of 11-ci s-retinoids by semi-hydrogenation of 11-yne-retinoid precursors with Cu/Ag- activated zinc dust.